Federal Republic of Germany Priority Application 101 52 543.5, filed Oct. 24, 2001 including the specification, drawings, claims and abstract, is incorporated herein by reference in its entirety.
The invention relates to a method of controlling at least one safety-specific function of a machine, where a monitoring region is monitored by at least one sensor and the monitoring region comprises a safety boundary, and a safety-specific function is triggered when an object passes beyond the safety boundary. The invention also relates to an apparatus for implementing the method.
In order to protect operators of potentially dangerous machines, such as, for example, presses, bending presses, robots and the like, various safety arrangements are known.
For example, in the simplest case, protection is provided by mechanically safeguarding access to, or intervention in, a danger region, for example by grilles or blocking fencing. A mechanical safeguard, however, also makes it more difficult to access machines in the danger area when the machines are at a standstill. As a result, optoelectronic protection arrangements are preferably used nowadays.
These optoelectronic protection arrangements may be constituted by a light-grille barrier which forms an optical access safeguard. Passage through the light-grille barrier triggers a safety-specific function of the machine, for example, stoppage of the machine.
Further optoelectronic protection arrangements are disclosed in WO 97/25568 and WO 00/67932. In order to protect fingers in bending presses, individual light barriers are arranged in the immediate vicinity of the bending tool. Thus, access to the press is ensured in principle and only the dangerous region in the immediate vicinity of the bending presses is protected by the light barriers.
All these optoelectronic protection systems have in common the fact that the boundary between the danger region, which is to be safeguarded, and a safe region is rigidly defined by a minimum distance from the area of potentially dangerous movement of the machine. When an object passes beyond this boundary, the safety-specific function, which typically means stoppage of the machine, is triggered. Since the machine requires a certain amount of time or distance to slow down, and the speed of the object which penetrates into the danger region is unknown, the protection arrangements (e.g. light barriers and light grilles) must be spaced from the actual danger zone by a sufficient distance. The spacing must be sufficient, for example, to ensure that even in the case of rapid movement, such as an operator falling, the machine still comes to a standstill in time before the operator could come into contact in anyway with the dangerous region of the machine. This safety arrangement does not distinguish between slow, careful movements of the operator and rash, and in some circumstances rapid, movements, which are more likely to result in an accident. For safety reasons the safety-specific function is always triggered.
According to one aspect the invention improved methods and apparatuses are provided by means of which the safety of a machine operator continues to be ensured and which trigger the safety-specific function in an improved manner taking into account the situation.
According to one embodiment of the invention, a method of controlling at least one safety-specific function of a machine is provided. The method comprises: monitoring a monitoring region with at least one location-resolving and time-resolving sensor, the monitoring region comprising a safety boundary which separates off a danger region and defines a safe distance from a danger zone of the machine; detecting at least one of a position, a movement direction and a movement speed of an object; establishing a position of the safety boundary in a variable manner depending on the at least one of a detected position, movement direction and movement speed of the object; and triggering the safety-specific function of the machine when entry into the danger region by the object is detected.
According to another embodiment of the invention, an apparatus for controlling at least one safety-specific function of a machine is provided. The apparatus comprises: at least one location-resolving and time-resolving sensor for monitoring an object in a monitoring region; an evaluating unit for determining at least one of a position, movement direction and movement speed of the object from sensor signals received from the at least one location-resolving and time-resolving sensor; a safety boundary unit for establishing a safety boundary in the monitoring region, the safety boundary separating off a danger region and defining a safe distance from the machine, the position of the safety boundary being established depending on the determined at least one of a position, movement direction and movement speed of the object; and a warning signal or switch for triggering the safety-specific function following a detected entry of the object into the danger region.
According to another embodiment of the invention a method of controlling at least one safety-specific function of a machine is provided. The method comprises: monitoring a monitoring region with at least one location-resolving and time-resolving sensor, the monitoring region comprising a safety boundary which separates off a danger region and defines a safe distance from a danger zone of the machine, and a safety region separate from the danger region; detecting at least one of a position, a movement direction and a movement speed of an object; establishing an extent of the safety region in a variable manner depending on the at least one of a detected position, movement direction and movement speed of the object; and triggering the at least one safety-specific function of the machine when entry into the safety region by the object is detected.
According to another embodiment of the invention an apparatus for controlling at least one safety-specific function of a machine is provided. The apparatus comprises: at least one location-resolving and time-resolving sensor for monitoring an object in a monitoring region; an evaluating unit for determining at least one of a position, movement direction and movement speed of the object from sensor signals received from the at least one location-resolving and time-resolving sensor; a safety boundary unit for establishing a safety boundary in the monitoring region, the safety boundary separating off a danger region and defining a safe distance from the machine; a safety region unit for establishing the extent of a safety region, separate from the danger region in the monitoring region, the extent of the safety region being established in a variable manner depending on the determined at least one of a position, movement direction and movement speed of the object; and a warning signal or switch for triggering the at least one safety-specific function following a detected entry of the object into the safety region.